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From: "msebor at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug tree-optimization/105585] [12/13 Regression] Spurious stringop-overflow warning with <atomic> since r12-4725-g88b504b7a8c5affb
Date: Tue, 17 May 2022 14:15:30 +0000	[thread overview]
Message-ID: <bug-105585-4-FA0VZlBHpC@http.gcc.gnu.org/bugzilla/> (raw)
In-Reply-To: <bug-105585-4@http.gcc.gnu.org/bugzilla/>

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105585

Martin Sebor <msebor at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
         Resolution|---                         |INVALID
             Status|NEW                         |RESOLVED

--- Comment #4 from Martin Sebor <msebor at gcc dot gnu.org> ---
The warning is caused by the if statement: if p is null, accessing the p->a
member is undefined.  It triggers because the GCC optimizer splits the code
into two branches: one with a nonnull p and another with a null p.  The second
one triggers the warning.

If p can be null then moving the increment to the body of the if statement
avoids the undefined behavior (and the warning).  If p cannot be null then
making the if statement unconditional also avoids the warning.

      parent reply	other threads:[~2022-05-17 14:15 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-05-12 16:58 [Bug c/105585] New: [12/13 Regression] Spurious stringop-overflow warning with <atomic> ed at catmur dot uk
2022-05-12 16:59 ` [Bug c/105585] " ed at catmur dot uk
2022-05-12 17:50 ` ed at catmur dot uk
2022-05-13  7:55 ` [Bug tree-optimization/105585] " rguenth at gcc dot gnu.org
2022-05-13 12:02 ` [Bug tree-optimization/105585] [12/13 Regression] Spurious stringop-overflow warning with <atomic> since r12-4725-g88b504b7a8c5affb marxin at gcc dot gnu.org
2022-05-17 14:15 ` msebor at gcc dot gnu.org [this message]

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